Manco Streaker Mini Bike

Well it would appear this turned into more than a new rear tire....





Haha, yepper! I figured it was time the ol' Teccy got some love, so I yanked it out and tore it down on the bench.

Got the cylinder head off, doesn't look too bad for the age of the engine:



Next I pulled the valves, since I figured on lapping them and doing some port work:



Then I got myself a mirror and some sandpaper and sanded the head down nice and flat:



I know I won't be taking enough off for much of a performance gain, but it'll help a little.

After sanding it 'til the high spots were gone I set it on the block to test the flatness. I found that was able to rock it maybe 0.001" with my finger so then I used the valve grinding compound to sand the head and the block together:



Turned out nice! Should be good and flat now.

Next came the port work. The stock ports were actually not too bad, so I just did some minor cleaning and made the inner bend a lot wider and smoother to free up some flow.

Before:



After:






Got the valves lapped and got a nice finish on them and the seats on the block:



I also figured on giving the cylinder a good hone, since there was no cross-hatching left and a little bit of scarring.

Before:



After:



Turned out pretty nice! Still just a hair of scarring left, but it shouldn't hurt anything. It's much better than before.

When I had the piston out I also noticed that the top compression ring was siezed:



I'm sure that wasn't helping performance, haha. But I ended up useing some penetrant and a screwdriver to get it freed up and springing nicely again. Then after some cleaning the piston went back in:



Didn't really check clearances like I should have, but the bearing surfaces looked onto be in beautiful shape so I didn't worry about it too much. After I torqued the rod bolts I got the block ready to go back together and put the cover back on:



Looking pretty freshed up!



Put the valves in next. Both springs got shimmed up with some washers:



Shouldn't be too much, I checked them at full lift and the springs aren't being compressed past their limit, so I don't think it will hurt anything.

Here's how she sits as of tonight:



Pretty happy with how things went! Gonna be cool to get it back on the bike and see how it does, haha. Tomorrow I'll get the head put back on with the new gasket, then I'm gonna try a bit of a timing advance to see if I get get a bit of a top end power boost. I'll most likely port the intake manifold a bit too before I put the carb back on.

Gonna be good I'm thinking! Got a new clutch coming for 'er too so hopefully I can put some power to the ground a bit better, haha. Let me know what ya think!

I've seen a lot of things, but I have never seen springs shimmed like that before. Interesting.

Engine looks all cleaned up well.

Just wanted to add a little stiffness. I've wanted to try it on an engine for a while, but never did it 'til now, haha.

Nice bit of rebuild there! I've also never seen springs like that before. Any ideas on what kind of tire you're going to get it?

Thanks! As far as finding a new tire for a 5" rim, I had no luck. But I did remember that I have a pair of little utility wheels with tires the same size as I need, so I ended up putting one of those on the front rim and swapping the good original one to the back. Probably gonna check online a bit to see if I can get one with the original tread.

Anyways, more engine work! Here's the finished head after the sanding and lapping. I also bit a small bit of work around the valves and shaved a bit of material to expose the spark a bit more:





Bought myself a goodie today too, since I wanna speed 'er up some:



Yep! Dropping from a 60 tooth sprocket to a 48 tooth on the rear. Should be a nice upgrade, haha.

Then I did some porting work on the little intake manifold, mostly smoothing out the bends and cleaning up the casting on the inside. Also took aways some material to make the engine side opening more round, as it had a funny flatspot in it:



Noticed a spot on the exhaust flange where it was blocking off the flow a little bit:



So I opened that up a bit as well.

Got the manifold bolted back up:



Then I took a shot at the timing advance. I couldn't do my filing trick with the coil because it was so thin on one side, so I actually just ended up removing the key and advancing it on the crank:



Not sure exactly how much it moved. Maybe about 0.045" or do, should be good for a couple degrees anyways. Well see how she likes it!

Oh, and here's the tire I'm putting on:





Not the best tire for this application, but it's much better than no tire at all. Haha. As I said though I'll probably look around online for one, this one will get me by for now.

Lastly I gave the carb a little bit of cleaning, and trimmed the limit tab on the butterfly shaft to get a couple extra RPMs:



When I first got it actually bent that tab a bit which freed up a couple RPMs, but if you bend it too far it hits a part of the carb and doesn't go back to idle. So I figured I cut it short and see what happens, haha.

Here she is as of tonight:



Going back together nicely!! I'm definitely thinking I'll be able to test fire it tomorrow the way things are going. Also I can do a bit of a break-in being that I honed the cylinder. Hopefully she wants to run good for me, haha.

Let me know what ya think!

Alrighty, good progress today!

Got the engine all assembled, and the rear wheel and sprocket reinstalled:





The engine was being finicky at first, might've been something to do with the timing advance. But either way, I eventually got it figured out and got 'er running good! Then after that I started re-mounting it in the frame, and hooking everthing up.

Test drive went well!!





Definitely noticed a difference in performance. The revs are nice and snappy, and there is a lot less bogging upon take-off and in rougher terrain than there was before. Real good low-end power it seems. Feels like a nice improvment to me!

I hit 28mph with it now, so I gained 5mph with the new sprocket in the rear. If I do a bit more tweaking to get to 30 it'd be pretty sweet, but I'm still happy with 'er now.

Oh I aso painted my choke mount to make it look less junky, haha.



Much better!

So I after I put some hours on the engine I dropped the oil while it was warm:



Pretty silver, but I expected that after the fresh hone job. I'll most likely change it again on the weekend.

Also gave the new plug a check while the oil was draining, to get an idea how it's burning:



Kinda hard to see the nice tanish colour in that picture, but it looks about perfect! Seems like everything is going well so far, so I'm happy with it. Gonna get a new clutch for it tomorrow to replce this worn out one and see how it acts after that. Should be good!

Let me know what ya think!

Got a new clutch for the little hot rod installed today:



Much better now. I tell ya this thing moves buddy, the take-off is a lot better with the impoved low end power of the engine and the new clutch, and at top end she really screams! I think I can hear the governor trying to back the engine off a bit when I hold it wide open, which is a little annoying, but it stops me from blowing it up I guess, haha. If I ever get sick of it I can pop the side cover off and yank the fly weights easy enough.

For now I'm loving the upgrades though! Can't wait to try and take down my cousins bike with it, hahaha.

Nice!  I see you even painted the spring blue.

Nice engine build! I seen the washer thing done on automotive heads when they rebuilt them. The idea there was to get the spring compressed to factory specs. Sometimes the spring would weaken over time so to bring the spring back to factory spec spring rate on a closed valve the rebuilder would shim up the spring to the right tension.

As long as you are not in coil bind, you are good. And with a little more tension on the spring too, to get rid of that nasty valve float.

The spark plug relief is a good idea done on the head. You can take it a step further, when servicing the spark plug, use a sharpy to mark the ground electrode position on the hex of the spark plug, so when you put the spark plug in you know that the ground electrode inside the cylinder is in the right position when tight.

MightyRaze wrote:

Nice!  I see you even painted the spring blue.

Thanks Mighty. Haha, yep it was getting a bit rusty so I had to freshen 'er up!

prancstaman wrote:

Nice engine build! I seen the washer thing done on automotive heads when they rebuilt them. The idea there was to get the spring compressed to factory specs. Sometimes the spring would weaken over time so to bring the spring back to factory spec spring rate on a closed valve the rebuilder would shim up the spring to the right tension.

As long as you are not in coil bind, you are good. And with a little more tension on the spring too, to get rid of that nasty valve float.

The spark plug relief is a good idea done on the head. You can take it a step further, when servicing the spark plug, use a sharpy to mark the ground electrode position on the hex of the spark plug, so when you put the spark plug in you know that the ground electrode inside the cylinder is in the right position when tight.

Thanks prancstaman! Yeah I was thinking of preventing valve float when I shimmed them up. I guess I can't really take full advantage of it until I completely remove the governor, but at that point I might wanna upgrade some internals anyways, haha.

Had the little bike back in the garage for some tinkering yesterday, unfortunately it wasn't running like I wanted it to:



But I went through the carb really good and sealed up the gasket surfaces, and she's doing good now!

Used my new temperature reader gun to check the head after a good run:



Bought that little unit on sale, quite handy!

Oh also my choke cable wasn't really working due to the cable holder being way too far from the carb, so I ended up making a  little mount that's much closer to the choke lever:



Works fantastic!

Then she was loaded up and taken out to the farm for some test running!



Found out I still can't out run my cousins bike, (He has a much newer unit with a 6.5hp clone on it) but at least I can keep up a little better now, haha.



Either way we had a great time ripping down the gravel roads! Once it dries up here we can do a bit more riding and what not,  should be lots of fun!

Well I've been ripping this little bug around quite regularly and having lots of fun, but I still don't think it's running quite like it should be. Always seemed like it was running on the lean side.

So I did some tinkering today and I found that if I spray carb cleaner at the welch plug in the side of the carb while the engine is running, it bogs significantly. I had the plug out to clean the carb a little bit ago and I guess it didn't seal up too well when I put it back in. Shoulda used a new one, haha. But all I did was use the good ol' Seal-All to seal up the area around the welch plug. We'll see how she acts tomorrow!

Hope you got it figured out!

Thanks, yeah it seemed like it helped. I can get it to idle so much better now. Before I had to have the idle kinda high just to keep it running.






Did a little bit of riding! She's a lot of fun to bomb around, haha.

I think I'd like to try and upgrade the carb next. I'd like there to be a little more power when I crank the throttle from a standstill. I saw a fella online who put a 6.5 OHV Briggs carburetor on one of these engines. Apparently it bolted right up to the manifold, so I just might have to look into that. Might be pretty cool!

Looking really nice allis! Makes me wanna mod my minibike some more!

Why thanks! Haha, yeah as it turns out it's quite fun to mess around with these little bikes.

Well the little mini bike is still running good, but these tires I've been using on the front aren't doing so well, haha. They were basically only designed for like a hand truck or something, but since they were for a 5" rim they were all I had that would fit this bike. Needless to say I'm on my second one and it's now blowing apart too.

Well I shouldn't be having the issue anymore because a package showed up at my house this morning!






Yep! Two brand new Carlisle 4.10 - 5 tires with the original tread style. Perfect! Even got some sweet stickers!

The plan is to throw a new one on the front and just keep the other one for a spare. I should have the new front tire installed this weekend!

Man, I never got stickers from them or jegs. <i'm jelly>

Haha, yeah I thought that was pretty neat.

Well I took a shot at swapping my new tire on this evening.

You can see the one I had on there had pretty much had it:





Not even that many miles on it!! Gonna have to look into that warranty I tell ya!

Anyway I got it all apart, got the rim split and the old tire off:



Got 'er on no problem! The split rims make it rather simple, haha.



Much better!



Feels better at speed that the other one, not as much vibration. Not surprisingly, those tires weren't exactly meant for this kinda speed, haha.

Shouldn't have any problems anytime soon now!

Looks good! That a snapper RER front tire? Actually i think snapper front rims are 4", not 5"

No Snapper lawn tractor tires here, these are high quality racing tires!!

Hahaha. Anyway I did a bit of screwing around with my chain tensioner today. The one I put on after the rear sprocket swap didn't have any real adjustment and I've had my chain pop off two or three times since then. So today I rigged up a quick one that has some adjustability:





Works great! No issues on the test run whatsoever. Definitely nice to have that issue fixed!

Well I'm still fighting some issues with the carb on this thing. I went through and cleaned it real good today, and that didn't help at all. Now it doesn't even want to idle for more than about 4 seconds. I'm wondering if she isn't sucking air aound the throttle shaft or something like that.

Either way I'm tired of screwing with it so I found a nice one online, and I ordered one this evening:



It has the adjustable main and idle jets too, which should be a very nice upgrade from the current fixed jet one.

Looking forward to getting it installed, I'll post an update as soon as it shows up!

Don't you love it when shipping is just as much as the item?

Haha, yeah that's how she goes I guess.

Alrighty so I got the new carb in the mail not too long ago, opened 'er up and it looked alright to me.



Came with a new gasket and a length of weird looking fuel line that I thought was a spark plug lead when I first opened it.

It bolted up fine with the exception of the choke shaft which I had to change to fit my application. No big deal though, I just swapped it from the old carb. I fought with it for a few days to get it to idle and run right, but today I finally got everything tuned up perfect and working good:



Definitely a huge improvment! Before the throttle response was pretty terrible, especially when the engine wasn't warmed up all the way. With the new carb though I can punch it and she really comes to attention and has a nice smooth top end! Quite happy.

Oh I also went and bought myself a real helmet, so I look a little less goofy when I'm rippin' around on this thing. Also it's probably much safer, haha.



Real happy with 'er now!



Next I need to install a kickstand so I don't have to lean it against stuff all the time, haha.

Let me know what ya think!

Nice! I like ones like that which have a shorter look than some of them. Looks a lot sportier that way. Glad the new carb worked out well. It's annoying as heck when you have running issues.